Input Voltage Threshold (VIH, VIL) Testing Technical Details

Publish Date: Jun 13, 2018 | 9 Ratings | 3.78 out of 5 | Print | 1 Customer Review | Submit your review

Table of Contents

  1. Section 1: Hardware Setup
  2. Section 2: Software Setup


This document will discuss the technical details of testing the voltage input thresholds on semiconductor devices using a test system created with the PXI platform. To learn more about the hardware components of this test system, click here. To learn more about the software components of this test system, click here

Voltage Input Thresholds are essential parameters that describe how a digital pin recognizes the outside world. Tests for voltage input thresholds can be used to make important distinctions about the characteristics of a device during validation, as well as the quality of a device during production test. These tests can be conducted on a wide range of devices from semiconductor chips to fully integrated consumer electronics devices. This paper will describe the process of testing the voltage input thresholds on a packaged semiconductor chip.

1. Section 1: Hardware Setup

The essential connections for performing voltage input tests using this PXI system are as follows: the PXIe-4141 must be connected to the VDD and VSS terminals of the chip to provide power, and 1) the SMU channel testing the pin must be connected to the pin either directly or through a switch, or 2) the PXIe-6556 must be connected to the digital lines to be tested. Additionally, feedback from the device must validate its current programmed state, requiring a single or multiple feedback lines to the HSDIO. A simplified example demonstrates a logical OR of several digital inputs, passing the status to a single digital output pin. In this example, any input pin with a high enough voltage value will result in a logic high in the output line.

Figure 1: VIH and VIL test setup.  Input voltage ranges from 0 V to VDD to determine transition points

Often in characterization, voltage to the input line is swept from VSS to VDD to determine the voltage at which the DUT receives a logic high. Similarly, voltage to the input line is swept from VDD to VSS to determine the voltage at which the DUT receives a logic low. However in production, a single voltage is provided to the input line to ensure that the DUT is capable of correctly registering that voltage as a high while another voltage point is provided to the line to verify a logic low reading.

The configuration shown above shows how both the PXIe-414x SMUs or PXIe-6556 PPMU can be used as the voltage source for pin under test. Like the other PC parametric tests, if the SMU is used for this test, the PXI-2535 matrix will be required to switch the SMU line to the appropriate pin to be tested.

Automated Test Steps

Step 1: Power the DUT by applying VDD

To power the DUT, the PXIe-4141 SMU should be set to output the rated voltage of the device (usually 3.3V). In addition to this voltage setpoint, it also very important to set a current limit to ensure that the DUT does not draw excessive currents if it is faulty or shorted.

Step 2: Condition the DUT into the appropriate state

Because the power draw can be affected by the state of a device, it is essential that the device is preconditioned to a known state prior to the power being measured. This preconditioning is performed by using the PXI digital I/O device to generate the appropriate pattern to put the DUT into the desired state.

In the case of a Gross IDD test, a conditioning pattern is not necessarily needed. To save time, power can be tested immediately after voltage is applied to the DUT in order to get a general idea of the device's consumption. In other cases, a reset pattern can be used.

Depending on the device, Dynamic IDD tests can require continuous patterns to be applied in order to keep the device active through constant stimulation. In this case, the power must be measured while the conditioning pattern is being applied.

In the case of an IDDQ test, multiple conditioning patterns can be applied sequentially and power is measured after each step. These patterns are designed to keep the device in a low-power or quiescent state while still activating and changing internal logic sections.

Step 3: Measure the Current

The next step is to measure the current draw of the VDD terminal using the SMU. It is important to consider the range and the resolution needed on the expected current measurement. For instance, a static IDD measurement can result in currents at or below 1uA, so it is important to use the SMU's lower ranges to achieve the necessary precision. In this case, the PXI-4130 can be set to its lowest range of 200uA in order to achieve 1nA current measurement resolution. Some devices may also have an associated settling time before the current draw stabilizes, so a delay can also be necessary prior to measuring.

Step 4: Calculate Power and compare

The final step is to convert the measured current into an associated power draw and compare that to the acceptable limit for a functional device. These limits are be both device dependent and state dependent.

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2. Section 2: Software Setup

The software for this Input Voltage Threshold test is developed using NI LabVIEW and NI Switch Executive. LabVIEW is used as the primary Application Development Environment (ADE) while Switch Executive is used to configure routes on the high-density matrix. For simplicity, this code only tests for the Voltage Input High (VIH) threshold. To add in a test for VIL, repeat the same steps, but sweep the SMU down from a high voltage to a low voltage and watch for the digital transition from high to low.

The following software versions were used to implement the Input Voltage Threshold Test:

LabVIEW 8.5Graphical Programming Environment

Switch Executive 2.1.1Switch Management Software

The LabVIEW code described in this document can be downloaded from the link at the top of this document.

Note: Functional blocks in the LabVIEW graphical programming language are known as ‘Virtual Instruments’ or ‘VIs’. The acronym ‘VI’ will therefore be used when describing procedures in this section.

The steps described use the configuration in which a PXI-2535 matrix switch is used to connect the PXIe-414x SMU to the pin to be tested.

Step 1: Initialize the PXIe-4141 based on the resource name, then set the utility channel to power your device by changing the voltage set point to the desired VDD. Also remember to set the current limit to the max allowable current in order to protect your device and test setup. Once all settings are configured, enable the output of the utility channel in order to provide power to the device under test.


Step 2: If necessary, add the digital I/O code here to condition your DUT to the appropriate logic state such that there is feedback of what a particular pin sees as a logic high. One example of this would be to make a single output pin be the logical OR of all input pins.

Step 3: Set the SMU channel on the PXIe-4141 to begin at 0V and have a current limit 200 µA for the subsequent tests. The voltage will be changed programmatically later.

Step 4: Initialize a session to the matrix switch via NI Switch Executive. The NI Switch Executive (NISE) Virtual Device Name is input to the Open Session VI to begin communication with all the switches in the system. The individual routes to each pin on the device under test are retrieved from the route group specified, and used later to make the connections. To download the "extract_routes" subVI and an example NI Switch Executive configuration, return to the software components section of this reference architecture.


Step 5: Connect the SMU to the pin under test and ground all other input pins using the appropriate switch routes. Next, configure the SMU to conduct a voltage sweep from 0 to 3 V. At each point in the sweep, test to see if the DUT has recognized a logic-high on the input. Continue until the DUT sees a logic-high value, or until the upper limit of the sweep has been reached.

Step 6: Measure the voltage value on the specified output channel of the SMU at the time that the DUT recognizes the logic-high. Alternatively, the last setpoint of the sweep can be used instead of teh measured value. Next, analyze the data to determine whether the pin passed or failed the Voltage Input Threshold test. If the voltage threshold is too high, that means that the chip requires a voltage too close to VDD in order to function, and is therefore faulty.

Step 7: Disconnect the switch channels that connect the SMU to the pin under test

Step 8: Show a histogram of the pin measurements and display the individual values in a table.

Step 9: Power down and close SMU session.

Step 10: Disconnect all switch channels and close switch session.

The front panel of the attached example code allows the user to control the settings of the SMU, Switch, and HSDIO instrument. It also presents test results for the Input Voltage Threshold test in a table and a histogram.


Additional Resources


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Customer Reviews
1 Review | Submit your review

Error in this document  - Jul 24, 2013

Hello, It seems that there is an error in this document ( The first section is almost related to another test (power consumption), instead of the Input Voltage Threshold (VIH, VIL) Testing. Please could you correct this problem ?

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